Apparatus for distilling petroleum oils



y 8, 1939. J. E. SCHULZE v 2,166,374

APPARATUS FOR DISTILLING PETROLEUM OILS Original Filed Aug. 24, 1925 3 Sheets-Sheet 1 mwlo EScJuuZze.

- July 18, 1939. I J. E, SCHULZE 2,166,374

APPARATUS FOR DISTILLING PETROLEUM OILS Original Filed Aug. 24, 1925 5 Sheets-Sheet 2 Tif alto'mmp' July 18, 1939. J. E scHuLZE 2,166,374

APPARATUS FOR DISTILLING PETROLEUM OILS Original Filed Aug. 24, 1925 3 Sheets-Sheet 3 Patented July 18, 1939 UNITED STATES PATENT OFFICE APPARATUS FOR DISTILLING PETROLEUM OILS Original application August 24, 1925, Serial No.

Divided and this application August 19, 1935, Serial No. 36,895

11 Claims.

This invention relates to apparatus for distilling petroleum oils, and in particular it relates to apparatus useful especially in the manufacture of lubricating oils by distillation under high vacuum.

Although capable of use in carrying out various different processes of oil distillation, the novel apparatus has been found very satisfactory to employ in the manufacture of lubricating oils by high vacuum distillation in accordance with the process disclosed and claimed in this applicants prior copending application Serial No. 52,118, filed August 24, 1925, now Patent No. 2,017,820, granted October 15, 1935, of which the present application is a division. Reference will be made hereinafter to the process of the aforesaid prior application as one example of how the novel apparatus of the present invention may be usefully employed in practice, but it is to be understood that this is only by way of illustration and that the practical utility of the invention is not limited to employment in connection with that process but is of much wider scope.

One of the principal objects of the invention is to provide an apparatus system wherein lubrieating oils may be produced by direct overhead distillation under high vacuum from charging stocks or materials of various kinds, the lubricating oil distillates thus produced being of excellent quality and, under optimum conditions, requiring no further refining, as by acid treatment or filtration, to render them finished lubricating oils.

A further object of the invention is to provide apparatus wherein lubricating oil distillates of the above character may be produced even from charging stocks of relatively very inferior grade containing malodorous and unstabilizing constituents, or yielding such constituents upon distillation, from which it was previously impossible to produce lubricating oil distillates sweet as to odor and taste and also color-stable.

These as well as other objects and advantages of the invention will appear more fully from the description hereinafter given, wherein the invention will be further explained by reference to certain concrete illustrative examples embodying the underlying principles involved, and will then be more particularly pointed out in the appended claims.

In general, the novel apparatus is intended more particularly for operation at distilling pressures not exceeding 25 millimeters mercury absolute or less. Operating at distillation pressures of this order of magnitude in accordance with the process disclosed in the prior copending application aforesaid, it is possible to obtain sweet and stable mineral oil distillates from crudes or residua of Widely differing character, including charging stocks so high in combined sulphur, nitrogen, organic acids, or complexes comprising some or all of such constituents that it was not previously feasible commercially to employ them as starting materials for lubricating oil manufacture. Specific examples of low grade crude oils of this type are given in this applicants prior copending application aforesaid. Also, in the case of somewhat higher grades of crude charging stock containing similar but substantial percentages of some or all of the objectionable constituents in question, difficulty was sometimes experienced in obtaining, even by the process of applicants prior Patent No. 1,448,709, granted March 13, 1923, lubricating oil fractions perfectly sweet as to odor and taste and not tending to darken in color or assume an undesirable cast after prolonged exposure to light or standing in storage for a considerable time. This instability and the other unsatisfactory characteristics of lubricating oil distillates previously obtained from such starting materials was due to the presence therein of organic acids or compounds of sulphur or nitrogen, or complexes of these, tenaciously held by the lubricating distillates notwithstanding the fact that such contaminating impurities were generally of substantially lower boiling point than said distillates. Reference to the foregoing is here made merely by way of example as indicating how the apparatus of the present invention may be usefully employed when operating on charging stocks even of very low grade in accordance with the process of applicants prior copending application aforesaid.

In general, the apparatus system of the present invention provides means whereby the mineral oil starting material employed as charging stock, or a large part thereof, may be vaporized and lubricating oil fractions condensed therefrom in such manner that separation of the desired lubricating condensates is effected with minimum exposure thereof to contact with the lighter vapors and gases which carry most of the deleterious contaminants whose presence in finished lubrieating oil is objectionable. Most desirably, the vaporization of the crude oil is accomplished by distillation under high vacuum (low absolute pressure) of the order of magnitude characterizing the process disclosed in the aforesaid copending application. In the best form of the invention, there is provision whereby any given lubricating oil condensate is maintained at a temperature not materially below that at which it was formed until after there is no further opportunity for contacting with the malodorous vapors and gases evolved in the vaporizer. Provision is also desirably made whereby differing degrees of vacuum are applied to the desired liquid condensate on the one hand, and to the uncondensed malodorous vapors and gases on the other, respectively, whereby removal of said vapors and gases from the vicinity of 'said condensate may be greatly promoted. and expedited with advantage.

In order to afford a full understanding of the principles of the invention, a typical apparatus installation embodying said principles will now be described in detail in connection with the accompanying drawings wherein Fig. 1 is a side elevation of such installation;

Fig. 2 is a plan of same; and

Fig. 3 is a view in side elevation of an installation similar to that shown in Figs. 1 and 2 but modified to permit employment of steam in the distillation. In all the views, parts are shown broken away and in section.

Referring to the drawings, l represents a horizontal cylindrical still supported above a heating furnace indicated generally at H which may be constructed and fired in any suitable manner to heat the still indirectly rather than by direct contact of flame with the still bottom. In the present instance, the still I0 is especially constructed for operation under extremely high vacuum (1. e. extremely low absolute pressure) of an order of magnitude corresponding to 25 millimeters of mercury (or less) absolute pressure. To this end the still is interiorly braced as, for example, in the manner illustrated in applicants prior Patent No. 1,448,709, dated March 13, 1923. In order to provide vapor offtake means of ample cross-sectional area, the still is equipped with a plurality of vapor offtakes l2, in this instance ten in number, of uniform diameter, leaving the still at uniformly spaced points along the length thereof. The vertical portion l2 of each of the vapor offtakes [2 is relatively very short in order to minimize refluxing of distillate to the still. To the same end, the remainder of each of the vapor offtakes is inclined downwardly from the vertical portion [2 toward the cooling coil l3 into which each offtake [2 leads. These cooling coils I3 are submerged in cooling water contained in a box or tank l4. Said cooling coils, one of which is provided for each ofitake l2, discharge into a large-diameter collecting header l5.

At I6 is a riser, one for each offtake l2, the risers l6 all entering a horizontal header II. From the header I1 two sets of vapor lines l8 and I9 extend upwardly a considerable distance above the header I1 and then bend downwardly to connect with cooling coils 20 and 2!, respectively, disposed in cooling tank M. In the present instance, there are three vapor lines I8 in one set and two vapor lines IS in the other set. The coils 20 and 2|, of which there are two in this case and which are of larger diameter than the lines l8 and i9, discharge into a collecting header 22 of still larger diameter.

The described arrangement of the vapor pipes l8 and [9 in sets discharging, respectively, into separate cooling coils 20 and 2| is in harmony with the general purpose of ensuring ample cross-sectional area at all points in the piping system leading from the still. This general purpose may be accomplished in various ways, of course, but the arrangement here shown by way of example is effective and satisfactory in practice.

The piping system just described, beginning with risers l6 and extending to header 22, constitutes parts of what may be conveniently termed the header distillate line or deodorizer system, further reference to which will be made hereinafter.

Provision is made for guarding against substantial condensation of vapors at the point where they leave the still and for a short distance therefrom. This is for the double purpose of avoiding refluxing to the still and also of minimizing opportunity for contact of the distillation vapors with liquid condensate formed therefrom. In other words, the object is to get the distillation vapors out of and at least a short distance away from the still before material condensation occurs, and then to effect condensation of the desired liquid products at a point where no refluxing of condensate to the still takes place, and under conditions such that the condensate and residual uncondensed vapors and ases are rapidly separated from each other so that absorption or solution of such vapors and gases by the condensate is practically prevented.

This object may be attained in various specific ways, but the arrangement here illustrated is a typical practical way of effectively accomplishing the result desired. In the installation here shown, the upper part of the still is covered with heavy heat insulation or lagging 23. Furthermore, each of the vapor offtakes i2, is similarly insulated not only over portion I2 but also over its downwardly inclined portion down to the point where the riser l6 branches off. Thus there is substantially no condensation in any of the offtakes l2 until that point is reached. In the present instance, the riser I6 is also shown insulated and the header I1 may also be insulated. But the advisability in any given instance of insulating said risers and header is determined largely by the prevailing atmospheric temperature. Similarly the vapor lines l8, l9, may or may not be insulated from where they leave header I! up to the point where they bend downward again, but in the present example they are uncovered and therefore air-cooled. The extent to which these parts, l6l9, of the piping system are insulated may of course be adjusted as required by seasonal temperature conditions. By such adjustment the vapors and gases in the ascending lines are on the one hand cooled sufiiciently to cause nearly all vapors of desired liquid products to condense, the proportion of such vapors escaping condensation and passing over through the deodorizer system being thus minimized; while on the other hand the cooling in said ascending lines is not carried so far that the deleterious vaporous or gaseous impurities are condensed or their absorption by the useful condensate favored.

The remainder of each oiitake l2, beyond the junction of riser i6 therewith, is freely exposed to air-cooling, because in this part of the system collects the desired liquid condensate and proper cooling thereof is advantageous.

Returning now to the header [5, liquid collecting in this header is discharged through rundown line 24 to one of the run-down or receiving tanks indicated at 25, 26, 21 and 28, there being four such receiving tanks in the battery here illustrated although of course the number may be greater or less as practical operating conditions require. Said receiving tanks are connected, respectively, by valved branches 25, 26 21 and 28 with the aforesaid line 24. A lookbox 29 is placed in a vertical portion of said line.

The header 22 into which the header-distillate lines I8 and I9 discharge is connected by line 30 with header-distillate receiving tank 3! which, for reasons that will appear hereinafter, may be relatively small as compared to the main receiving tanks. A look-box 32 is provided in a vertical portion of line 3!], and it is also convenient to provide a sampling device 33 which is connected by valved pipe 34 with line 3!], and is also provided with a valved bleeder inlet 35 and a valved draw-01f pipe 36.

The entire distilling system is maintained uncler the desired degree or degrees of vacuum by means of a vacuum pump equipment indicated conventionally at 31, this equipment being either a single vacuum pump of suitable size or a double or triple stage pumping equipment, as may be found most desirable in any given case. The intake of the vacuum pump system has a valved connection 38 to the main vacuum line 39--4Il in which header-distillate receiving tank 3! is placed. The four main receiving tanks are connected to said line 39 by valved pipes 4!, 42, 43 and 44, for a purpose that Will appear hereinafter. Said pipes extend somewhat above vacuum line 39, as indicated at 45, before entering the same, thus providing against accidental entry from said vacuum line into any of the main receiving tanks, when the valves may be open, of liquid impurities that may collect in said vacuum line.

All seams and joints throughout the apparatus system are made absolutely tight, most desirably by arc-welding, thus making it possible to operate at extremely low absolute pressures and to maintain non-oxidizing conditions during the distillation. Mercury manometers for observing the prevailing absolute pressure are provided at different points in the system as indicated, for example at IIl for the still, at 25 26 21 28 for the main receivers, and at 3! for the header-distillate receiver 3!.

In order to illustrate further the principles of the invention, a detailed description will now be given showing how the described apparatus may be employed, for example, in manufacturing lubricating oils from Nevada County (Arkansas) crude in accordance with the process disclosed in the prior copending application Serial No. 52,118 aforesaid. A typical Nevada County crude has a gravity of about 14 Baum as a rule, and ordinarily contains 3% of sulphur or thereabouts. This crude contains practically no gasoline, naphtha or kerosene, the first runnings being gas oil of around 29 Baum gravity.

If the crude contains more than one-half of one per cent moisture, as it sometimes does, it should first be dehydrated to reduce the moisture content to that proportion or less. This dehydration may be accomplished in various ways known in the art and therefore the operation need not be described here. The crude, sufficiently free from moisture, is charged into the still Ill up to about 80% of the cubic capacity thereof and the still is gradually heated up to within 10 F. or so of the temperature at which the crude has been found by preliminary test to boil initially under 5 mm. mercury absolute pressure. This temperature is usually about 350 F. with the usual run of Nevada County crude.

This temperature having been attained, the distilling system is then placed under vacuum by operation of the vacuum pump system indicated at 3'! which, as already explained, may comprise as many single or multiple stage dry vacuum pumps as are found desirable to use in practice. This vacuum is applied to the still, main receivers and other parts of the system through the line 39 and, by way of header-distillate receiver 3!, through the header-distillate or deodorizer lines I8, I9. At the outset, the valves connecting the main receiving tanks with run-down line 24, that is, valves 25!, 26!, 21!, and 28!, are all open. So also are valves 30! and 40!. Valve 44! in pipe 44, and also valves 4, 42! and 43!, are closed. When the absolute pressure in the still has been reduced to about 10 mm. absolute, as measured by the manometer lo the initial distillate of gas oil begins to come over. At this stage, valves 26!, 21!, and 28! may be closed, if desired, assuming that the gas oil is to be collected in receiver 25. By reference to the indicating manometers, it will be found that the pressure in the still I and the header-distillate receiving tank 3! is substantially the same, while the pressure in the receiving tank 25 is slightly higher. In practice this difference in pressure should usually amount to some four or five millimeters during the first part of the gas oil out in order that a relatively large quantity of hot oil vapors may be immediately pulled over into the deodorizer system to warm the latter up promptly and get it to functioning properly. Later on, the pressure difference becomes less until by the end of the gas oil out it may have decreased to only about one millimeter. It will be found that a considerable quantity of liquid header-distillate collects in the receiving tank 3!, this distillate being characterized by very foul odor and a strong bluish phosphorescent cast. It is characteristic of this header-distillate that if only an extremely minute quantity thereof is added to a good lubricating oil it will adversely affect the cast of the oil and render the oil unstable. This distillate collecting in receiver 3! While the gas oil out is being taken off consists itself largely of light gas oil fractions containing a very large proportion of the total quantity of the objectionable malodorous and unstabilizing constituents contained originally in the crude, the removal and separation of which is one of the principal objects of the invention. The liquid caught in receiver 3!, therefore, comprises relatively low-boiling constituents which escape condensation in the risers I3, header I! and the ascending portions of header-distillate lines I8, I9, and are rapidly drawn off or sucked away from the heavier constituents which are condensed in that portion of the system and which flow thence through cooling coils I3, header I and run-down line 24 to the receiver tank 25. This separation of the lighter contaminating impurities from the desired liquid condensate is materially favored by the before-mentioned pressure differential which tends to cause flow through the deodorizer lines I8, I9, in preference to flow directly to the receiving tank 25 through the cooling coils and run-down line. This tendency of course affects not only the uncondensed vapors and gases in said lines I8, I9, but also to some extent the liquid condensate formed therein and in the risers I6. But in the case of said condensate this tendency is almost entirely overcome by the action of gravity so that notwithstanding the slightly higher suction or vacuum in the header-distillate lines, comparatively little liquid condensate is carried over as such through said lines provided the height of the overhead piping system l6, l1, I8, is properly adjusted and the lagging or heat insulation is also properly adjusted. This of course is governed to a large extent by the prevailing atmospheric temperature and varies with different seasons of the year. In practice, it is only necessary to have the piping system !6, IT, !8, extend high enough from main vapor line !2, to en sure adequate condensation at the maximum seasonal temperatures to be encountered, and then to increase the amount of lagging as may be necessary to compensate for decrease of temperature in winter. When the system is operat ing, the risers l6, headers l1, and ascending portions of lines !8, !9, should be quite hot, so that during the first part of the gas oil out considerable gas oil passes over into the header-distillate receiver 3!; and at all times these ascending lines should be so warm that the condensate formed therein is not cooled far below the condensing temperature. In this way the tendency for malodorous vapors and gases to be re-absorbed or dissolved by condensate flowing down the inner walls of the headers to the line !2 is minimized. It will therefore be seen that in the arrangement and mode of operation described, the hot still vapors and gases pass upwardly in countercurrent contact with downwardly flowing liquid condensate, the hot condensate leaving the base of risers !6 relatively free from volatile contaminants.

It may be noted here that when the apparatus is functioning properly or to best advantage, a fog is distinctly discernible in the look-box 32 in line 3!! leading to the receiver 3!; while no fog is discernible in look-box '29 in the run-down line 24. This condition exists When the absolute pressure in the still I0, and deodorizer system, including header-distillate receiver 3|, is somewhat lower than the pressure in receiver 26, 26, or 21, whichever one of these receivers may be in use at the time, and such pressure differential can readily be maintained by properly setting the control valves in the connections to the vacuum pump so that the pump pull is wholly or mainly through the deodorizer system.

Thus far the discussion has dealt only with the initial or gas oil out. The distillation of gas oil continues until a test sample of condensate taken from run-down line 24 through sampling device 24! (similar to sampling device 33) shows a flash point which has been selected as proper to determine the conclusion of the gas oil out. For example, this flash point may be selected as 290 F. in a typical instance. At this point the still temperature is ordinarily about 450 F. as indicated by a pyrometer P having its thermocouple located about one inch above the bottom of the still. This marks the beginning of the lubricating distillate out. In the meantime the operator has cracked or slightly opened valve 42! controlling line 42 which connects receiver 26 with vacuum. line 39, this being done before valve 26! is opened. In this way the pressure in receiver 26 can be reduced to that existing in receiver 25 at the end of the gas oil out, say 6 millimeters for example. This having been done, the operator now closes valve 42!, opens valve 26!, and closes valve 25!, whereupon the stream of distillate fiows into receiver 26. By this time it is no longer necessary to maintain as large a pressure differential as 4 or 5 millimeters because by far the greater part of the objectionable impurities have now been pulled over through the deodorizer system during the initial distillation which is intentionally forced somewhat, as by rapid firing, in order to bring about an immediate heavy rush of vapors through the deodorizer system, as described. Therefore after this initial rapid rush of vapors has been continued until a couple of hundred gallons of header distillate has collected in tank 3!, the system. may then be operated with a much smaller pressure differential, say one millimeter or thereabouts. To this end the proper control valve 4! I, 42!, or 43!, as the case may be, may be opened very slightly, if necessary.

The cut collected in receiving tank 26 may, if desired, be the entire quantity of lubricants that can be distilled from the particular crude undergoing treatment up to the temperature where substantial decomposition or cracking begins to take place in the still. However, it is usually more convenient to divide this lubricant yield into two or more portions or cuts, and in the present instance it will be assumed that the lighter portion, cor-responding to light and medium motor oil, is collected in receiving tank 26 and a heavier portion, corresponding to heavy motor oil, is collected in receiver 21. Thus, when the gas oil has been taken oiT as described and the succeeding lubricating distillate has been cut into tank 26, the distillation may be continued at an absolute pressure which has by this time been reduced usually to around 4 to 6 millimeters of mercury in the still and which may decrease gradually to as low as 1.5 to 3 millimeters toward the end of the distillation. After the gas oil has all been distilled off, it is found that the proportion of distillate that continues to come over through the deodorizer lines l8, l9 and collect in receiver 3! is relatively very small indeed, quite commonly amounting to as little as one-half of one per cent by volume of the crude initially charged into the still for the entire remainder of the distillation, and being substantially less foul than the header distillate obtained during the gas-oil cut. This latter part of the header-distillate may therefore be collected separately and re-run if desired. On the other hand, the quantity of header-distillate obtained during the gas oil cut amounts frequently to as much as 5 per cent of the initial charge of crude. In this connection it must of course be borne in mind that this 5 per cent is largely gas oil which, in association with the small percentage of deleterious impurities to be eliminated, is

carried over through the deodorizer lines because of the rapid rate of distillation and heavy pump pull on said lines at the beginning of the distillation, as above described. Until the still temperature as indicated by pyrometer P reaches about 630 F., the vacuum control valves are adjusted as may be necessary to maintain the before mentioned foggy appearance in the headerdistillate line look-box 32, thus ensuring always a slightly lower pressure in said line and in the still than in the particular receiver into which the distillate stream may be flowing.

In a typical instance, the lubricating distillate is run into tank 26 until the flash point of a test sample is about 380 F., at which stage the still temperature approximates 550 F.; but it is to be understood that the selection of the point at which to cut the distillate into tank 2'! may be varied as plant operating conditions require.

The lubricating oil distillate having been cut into receiver 21, the distillation continues as described with usually some further lowering of the absolute pressure, down to say 1.5 to 3 millimeters as observed in the still, which means a slightly higher pressure (e. g. 2.5 to 4 mm.) in receiver 21 as indicated by the manometer 2T The distillation is continued, running the lubricating cut into receiver 2'! until tests of thedistillate indicate that the point has been reached where decomposition or cracking is taking place or is about to take place in the still. The approach of this point is indicated when the flash point of successive test samples becomes stationary instead of gradually increasing as was the case during the earlier stages of the distillation. After remaining'practically stationary for some time, the flash point of test samples will be found to be gradually lowering instead of increasing, and at this point it is best practice to out the distillate into receiving tank 28. The still temperature is now approximately 630 F., and since cracking has now begun, it is desirable to complete the distillation as rapidly as possi ble. Accordingly valve MI is now opened wide and the full pull of the pump is exerted through the large pipe connection 44 and receiver 28 directly upon the run down line 2 5, a procedure which immediately causes a substantial increase in the size of the stream coming through line 24. Hardly any distillate other than normally fixed gases comes over through the deodorizer line from now on.

The distillation can be continued up to whatever maximum distillation temperature is found in practice to be commercially advantageous, notwithstanding the fact that the lubricating fraction thus collected in receiver 28 contains cracked products and is therefore not as high in grade as the oil collected in receivers 26 and 21.

The residue remaining in the still in after the distillation has been run as described, is asphaltic in character and may be either a hard or soft asphalt, or a flux oil, depending upon the extent to which the distillation is carried. All of these products are valuable commercially, and the particular form in which it is desirable to obtain the residue in any given instance may to a considerable extent be determined by market conditions existing at the time.

The gas oil fraction collected in receiver 25 may be considered to be a finished product and disposed of as such.

The lubricating oil cuts in receivers 26 and 27 are good lubricating oil products but still contain a small proportion of organic acids which should be removed in order to render the products perfectly sweet, clean, and stable. Accordingly, these cuts are most desirably re-run in a manner to be described presently.

The heavy lubricating distillate contained in receiver 28 also contains organic acids but in addition is further characterized by an appreciable content of cracked products resulting from decomposition of the oil in the still at tempera tures above about 630 F. This heavy lubricating out is therefore also re-run to obtain finished products.

The re-running of the several cuts contained in receivers 26, 21 and 28 may be conducted in the same manner in each instance if these cuts are re-run separately. It is not essential, however, that they be separately re-run, but on the contrary the entire yield of lubricants obtained in the first distillation may be either collected or mixed together and re-run as a whole. There are certain marked advantages, however, in rerunning the several cuts separately, and this method is therefore to be recommended in practice. A description of how any one of these cuts is re-run will sufiice for .all.

In order to eliminate organic acids and traces of other impurities that may be contained in the cut to be re-run, the oil is now treated with a neutralizing agent having the power to react With the organic acids and with such other impurities as may be present in such manner as to enable substantially complete elimination and separation thereof from the oil in the re-run distillation. Various neutralizing agents may be employed for this purpose, but a caustic alkali, such as caustic soda, is effective and convenient to use and is therefore preferred. Examples of other basic reagents that may be employed, however, are soda ash, lime, and the like. In using caustic soda as a neutralizing agent, this may be employed in a water solution of say 30 to 40 Baum strength. Assuming a 40 Baum solution, it is found sufficient to employ about a pint of the solution for each barrel of lubricating oil distillate to be re-run. The exact amount may vary somewhat depending upon the nature of the starting material. Such a proportion of the solution having been added to the charge of oil, the charge is then thoroughly agitated, as by blowing in air, or otherwise, until the neutralizing agent has been uniformly distributed through the charge. The charge is then re-run in apparatus which may be of exactly the same character as that shown in Figs. 1 and 2 and hereinabove described in detail. The re-run distillation may be carried out in precisely the same manner as the first distillation except that the particular cuts of lubricating oils made may be difierent from or more numerous than those of the first distillation, it being convenient ordinarily to so determine the cuts as to obtain .a range of finished oils corresponding generally to commercial types of oils demanded by the trade.

In thus re-running the lubricating oil distillate initially collected in receiver 26, a certain further quantity of non-viscous distillate is obtained of which the viscosity ranges from 60 to seconds at F., but the proportion is relatively very small. A somewhat larger amount, approximating say 10 per cent, is also obtained in rerunning the heavy cracked lubricating distillate initially collected in receiver 28. The residues remaining after re-running the distillates initially collected in receivers 20, 21 and 28 are accumulated, and when the accumulation is suiiicient it is also re-run in the manner already described and approximately 90 per cent of the accumulation is recovered as valuable lubricants. The final residue from such re-run of accumulated residues may be disposed of as fuel oil or otherwise as may be desired.

While the dimensions of the various parts of the apparatus system herein disclosed may of course be varied widely in practice within the scope of the invention, the dimensions and capacities of the more important parts of one form of apparatus installation that has proved elfective and satisfactory in practice will be given by way of illustration but not at all by way of limitation. In this typical installation, horizontal cylindrical still i0 is nine feet in diameter and thirty feet long, giving an approximate charging capacity of about 250 barrels of 42 gallons each. Each of the ten offtake lines l2 has an internal diameter of ten inches, and the vertical portion l2 thereof rises to a height of about eighteen inches above the still, it being desirable to have this height as small as conveniently possible. Each of the cooling coils 13, into which the offtakes I2 discharge liquid, is a three-inch pipe; and the header l5 into which the ten cooling coils l3 discharge is ten inches in diameter, as is also the run-down line 24 leading to the horizontal cylindrical receivers 25, 26, 2? and 28, each of which latter is in this instance seven feet in diameter by sixteen feet long.

Each of the ten risers I6 is six inches in diameter, and extends upward ten feet to enter the header H, which is eight inches in diameter. The five deodorizer lines l8, l9, are of four-inch pipe and extend ten feet higher. The cooling coils 20, 2|, into which the lines l8, l9, discharge, are sixinch pipes; and the header 22 is ten inches in diameter as is also the line 30 leading therefrom to the small receiver 3| which is four feet in diameter and sixteen feet long. The vacuum line 39, 4!), is ten inches in diameter as is also the pipe 44 leading therefrom to run-down tank 28. The pipes 4|, 42 and 43 connecting tanks 25, 26 and 21 to vacuum line 39 are four inches in diameter; while the pipes 25 26 21 and 28 which connect said tanks with run-down line 24 are six inches in diameter.

In general, it is important that the piping connections, both vapor and liquid lines, between the still and the vacuum-producing means, shall be of such ample capacity as to favor free and substantially unobstructed pull of the vacuum-producing means upon the still at all stages and under all conditions of normal operation. It is also important that the vacuum-producing means be able at all times to exert a direct and free pull through the cooling coils and associated piping upon the receiving tanks; but is is also desirable that the arrangement shall be such that the pull of the vacuum-producing means upon the still can be maintained slightly greater than the pull of said means upon the receivers, thus creating a pronounced tendency for the distillate from the still to flow toward the vacuum pump by way of risers and overhead lines l6l8 as already described and for the purposes set forth. This object can be achieved in various different ways, but in the specific arrangement and design of the apparatus herein disclosed it is achieved at least in part by reason of the fact that in pulling upon the receiving tanks 2528, the action of the vacuum-producing means is to some extent affected by the liquid in the cooling coils l3 which, although by no means filling said coils in normal operation, probably exerts a slight throttling action.

Fig. 3 illustrates how the apparatus system may be arranged where the distillation is to be carried on with the aid of steam, most desirably superheated, introduced into the charge through valved pipe S. In this arrangement, the overhead vapor lines l8 lead to a cold condenser indicated generally at M, there being most desirably a separate condenser coil 20 for each of the lines l8. The water in condenser tank 14 should be maintained substantially cooler than that in tank M. In the coils 20, both steam and oil vapors condense and are then discharged into header 22', from which the liquid products are conveyed by line 30' to a receiver 3|. While only one receiver 3| is here shown, it is sometimes desirable in practice to employ two such receivers into which the liquid products may be directed alternately in order that the condensate may be more readily removed from time to time without disturbing operation of the system as a whole. It is also sometimes desirable to operate with two or more such receivers 3| in series. Whether one or more of these tanks 3| be employed, it or they should be kept cold, but not below the freezing point of water, by suitable cooling means such, for example, as cooling coils C through which a cooling medium of any suitable character may be continuously passed.

From the receiver or receivers 3|, the vacuum line 39, 40, extends to the vacuum pump 31 as before described, the system as a whole being similar, except in the particulars above noted, to that illustrated in Figs. 1 and 2.

In the specific example hereinabove given, illustrating how the method of the invention may be practiced with the aid of the apparatus shown in Fig. 1, the manufacturing procedure involves two distillations, namely, a first distillation of a crude without the addition thereto of a neutralizing agent but with separation of a large proportion of the malodorous and other impurities as described; and a second or re-run distillation of the lubricating distillate or distillates in the same manner but with the addition of a neutralizing agent, such as caustic alkali, to the oil that is to be so re-run. However, it is not to be inferred that successful employment of the novel apparatus is restricted to a procedure involving two or more successive distillations. On the contrary it is feasible and in some cases advantageous to add a neutralizing agent directly in the first instance to the crude or residuum used as starting material and to distill over finished lubricating oil products directly without the necessity of re-running. However, where the crude or residuum employed as starting material is an asphaltic base material, it is ordinarily desirable not to add a neutralizing agent directly thereto because this would decrease the value for many purposes of the asphalt residue left in the still at the end of the distillation. By using a two-stage procedure of the character hereinabove described, this difliculty is avoided, an asphaltic residue free from alkali being obtained from the first distillation, while the presence of alkali in the final residuum resulting from the last of the re-run distillations is not objectionable since this residuum is not asphaltic and is useful only as a fuel oil. Where the crude or residuum employed as starting material is non-asphaltic in character and yields a distillation residue in which the presence of alkali is unobjectionable, or where it is feasible commercially to dispose of an asphaltic residuum containing alkaline matter, the foregoing considerations are not so important, and it is therefore practicable in some cases to manufacture finished products direct by a single distillation from the crude starting material.

Nor is it to be inferred from the specific description hereinabove given that the invention is restricted to batch or intermittent distillation. A method involving batch distillation has been described hereinabove merely for purposes of i1 lustration and it is entirely feasible to employ a battery of stills through which the oil passes successively, each still yielding a distillate having characteristics determined by the conditions uner which that still is being operated.

Where the starting material is a crude oil containing a rather large proportion of gas oil, say

25 to 30 per cent, such as Smackover crude for example, or where the crude contains a considerable proportion of other relatively light fractions such as gasoline, naphtha and kerosene, it is feasible to top the crude in an ordinary pipe still or steam still down to a point where the residue has an initial boiling point of around 300 to 350 F. at to 101 millimeters absolute pressure. This of course involves the use of temperatures in the topping plant of 575 to 600 F. or thereabouts, operating under atmospheric pressure.

The invention is also applicable to the treatment of parafiine base crudes and residua, but in treating such starting materials it is necessary to guard against clogging of the vapor lines, cooling coils, etc. with congealed wax. This can be readily done as by steam-jacketing the apparatus parts in question and also maintaining the receiving tanks warm so that the condensates collecting' therein can be removed and suitably treated for separation of contained wax by centrifuging or other appropriate method.

In using the apparatus for the manufacture of lubricating oils, conducting the distillation, whether in one stage or more than one stage, under strictly non-oxidizing conditions is a matter of vital importance for attainment of satisfactory results. Every precaution should be taken to ensure absolute tightness of the apparatus by welding all joints and seams as already stated. C'ontinual leakage of even a relatively very minute quantity of air into the system can seriously affect the proper operation of the process and result in production of inferior products. It is also im portant to avoid as far as possible refluxing of distillate to the still since this results in discoloration and other damage to the lubricating products by cracking or otherwise prior to attaining still temperatures around 630 F.

It is feasible to use other types of oil-Vaporizers than the horizontal cylindrical still type herein disclosed by way of illustration. Thus, for ex-- ample, pipe stills operating in conjunction with appropriate dephlegmators or separating drums of construction suitable to withstand the use of extremely low absolute pressures, can be used to advantage in some cases.

It is to be especially noted that the present in-. vention makes possible the manufacture of good finished lubricating oils as direct overhead distillates from any crude, residuum, or other heavy mineral oil material, no matter how high may be its content of sulfur, organic acids or other contaminating impurities, and that no acid treatment, filtration, or other additional finishing treatment is required to produce high grade lubricants of the best color, greatest stability and other desirable characteristics.

It is of course possible to operate the novel apparatus in ways quite different from that hereinabove described. For example, the suction or pull of the vacuum-producing means through the various lines or pipes can be so adjusted that, if desired, relatively heavy oil vapors may be caused to pass on down through that portion of lines l2 extending laterally beyond the base of risers 16 (to the right thereof in the drawings), and thence to header l5 through cooling coils l3, which coils, under these particular circumstances, function also as condensing means. Operating the apparatus in this way is ordinarily not to be recommended, however, since it gives much less desirable results than are obtainable by operating the apparatus as in the manner previously hereinabove set forth.

What is claimed is:

1. Apparatus for refining oils comprising, in combination, an oil vaporizer, vapor-offtake means leading therefrom, conduit means extending upwardly from said offtake means and constituting a reflux condensing zone, means for adjusting the cooling effect produced in said zone, other conduit means extending downwardly from said ofitake means, separate receivers into which said conduit means respectively discharge, vacuum-producing means communicating with said receivers, and means for separately adjusting the pull of the vacuum-producing means on the respective receivers.

2. Apparatus for refining oils comprising, in combination, an oil vaporizer, an upright cooling device, a vapor-oiftake leading from said vaporizer to said cooling device, separate conduit means for conducting, respectively, uncondensed vapors and gases from the upper part of said cooling device and condensate from a lower part, separate receiving means into which said conduit means respectively discharge, vacuum-producing means connected to said receiving means, and means for adjusting the pull of the vacuum-producing means on the respective receiving means, separately.

3. Apparatus for refining oils comprising, in combination, a still, a plurality of heat-insulated vapor-ofitakes leading therefrom, a cooling riser extending upwardly from each offtake, a plurality of vapor lines and cooling coils connected to the upper portions of said risers, the piping system comprising said risers and vapor lines being adjustably heat-insulated, a plurality of run-down lines and cooling coils connected to the lower portions of said risers, separate receivers into which said vapor lines and their associated cooling coils, on the one hand, the said rundown lines and their associated cooling coils, on the other, respectively discharge, and vacuumproducing means connected to said receivers.

4. Apparatus for refining oils, as set forth in claim 3, further characterized by the provision of means whereby the effective pull of said vacuumproducing means through the vapor lines and the run-down lines, respectively, may be separately adjusted and controlled.

5. The combination of a still, vapor outlets: therefrom, branch pipes from said outlets extending respectively laterally and upwardly and through which respectively heavier and contaminating lighter vapors escape, a header with which said upwardly extending pipes communicate, pipes each extending respectively upwardly and thence downwardly from said header, a header with which the last named pipes communicate, and condensing means with which said laterally extending pipe and said second header communicate.

6. The combination of a still, vapor outlets therefrom, branch pipes from said outlets extending respectively laterally and upwardly and through which respectively heavier distillation products and lighter contaminating distillation products escape, a header with which said upwardly extending pipes communicate, pipes each extending respectively upwardly and thence downwardly from said header, a header with which the last named pipes communicate, and cooling means with which said laterally extending pipe and said second header communicate.

7. The combination, with a still having a plurality of vapor outlets, of vapor oiftake pipes, one for each outlet, each offtake pipe branching into (1) a pipe extending upwardly into which vapors and gases, including both relatively heavy vapors and also relatively light contaminating vapors and gases, pass from said still and (2) a second pipe extending downwardly into which passes, from said upwardly extending pipe, liquid oil condensed from said relatively heavy vapors, a header into which each said upwardly extending pipe communicates, additional pipes each extending upwardly from said header and thence downwardly, said additional pipes being cooled sufiiciently to efiect condensation, in their ascending portions, of such relatively heavy oil vapors as ascend thereinto from said header and. from the first-mentioned upwardly extending pipes, and cooling means with which each said second downwardly extending pipe and said additional pipes communicate.

8. The combination, with a still having a pluralit-y of vapor outlets, of oiftake lines, one for each outlet, connected to said outlets and sloped downwardly away therefrom, a corresponding plurality of risers, each extending upwardly from one of said sloped ofitake lines at a point intermediate the ends thereof, a header connecting the upper ends of said risers, overhead lines extending upwardly from said header and then downwardly, that portion of said ofitake lines between the still and said risers being heat-insulated, and said risers, header and overhead lines being sufliciently exposed to ensure condensation therein, at locations in advance of the downwardly extending portions of said overhead lines, of relatively heavy oil vapors coming from the still at any given time, but insufiiciently cooled to permit condensation of contaminating lighter vapors therein at said locations, cooling means connected to the lower ends of said sloped ofitake lines and to the lower ends of said overhead lines, and exhausting means connected to said cooling means and adjustable to exert a greater pull through said overhead lines than through the lower portion of said sloped offtake lines, whereby to draw all vapors and gases up into said risers.

9. Apparatus for manufacture of lubricating oils by distillation under high vacuum which comprises, in combination, an oil vaporizer, reflux condensing means connected thereto and arranged to receive vapors therefrom, separate conduit means arranged to lead condensate and uncondensed vapor, respectively, away from said condensing means, separate receivers into which said separate conduit means respectively discharge, vacuum-producing means connected to said receivers above the liquid level therein and operable to maintain absolute pressure below 25 millimeters absolute throughout the foregoing system, the paths by which condensate and uncondensed vapors separately travel being wholly unconnected between said condensing means and both said receivers, and means for adjusting the pull of the vacuum-producing means on the respective receivers, separately.

10. Apparatus as defined in claim 9, further characterized by the fact that said conduit means are of such large diameter as to provide vapor space for the free pull of said vacuum-producing means on the vaporizer.

11. The combination, with still means, of a plurality of vapor offtakes leading therefrom, reilux condensing means into which each off take is arranged to deliver vapors and gases from said still means, a vapor line arranged to conduct uncondensed vapors and gases from each said condensing means, cooling means into which such vapor lines lead, a receiver connected to said cooling means, a liquid condensate line leading from said condensing means, a receiver connected to said liquid condensate line, vacuum-producing means connected to said receivers, and means for adjusting the pull of said vacuum-producing means on the respective receivers, separately.

JOHN E. SCHULZE. 

